Cellulose is a polysaccharide compound with the formula (C6H10O5)n consisting of a linear chain of several hundred to over ten thousand β(1→4) linked D-glucose units joined by an oxygen (ether) linkage to form long molecular chains that are essentially linear. Cellulose may be decomposed to glucose by the enzyme cellulase, and, in an alternative process, it may be hydrolyzed to glucose. The degree of polymerization for cellulose may range from about 1000 for wood pulp to about 3500 for cotton fiber, giving a molecular weight from about 160,000 to about 560,000. Being naturally formed by plants, cellulose is the most abundant organic polymer on Earth. Conversion of cellulose from crops into biofuels such as ethanol, has been developed as a fuel source process alternative to traditional sources such as refining oil and gas. Glucose sugar may also be used for fermentation.
The efficient hydrolysis of cellulose to form fermentable sugar will open up vast natural resources for the production of biofuels. Cellulose consists of crystalline and amorphous regions. By treating it with a strong acid, the amorphous regions can be broken up to produce crystalline cellulose. The slow step in converting cellulose to fuel is the hydrolysis. It is particularly slow for crystalline cellulose since crystalline cellulose is not soluble in water.
U.S. Pat. No. 4,250,306 relates to a process for preparing swellable cross-linked carboxyalkylcelluloses by reacting cellulose, a carboxyalkylating etherifying agent, and a cross-linking agent in an aqueous alkaline medium, comprising effecting alkalizing, etherifying, and cross-linking simultaneously in one reaction step using fibers, textile sheet materials containing these fibers, or sheet materials of other kinds, having a base of cellulose hydrate or of natural cellulose, by contacting said fibers or sheet materials with an ample quantity of an aqueous alkaline reaction mixture, removing part of the reaction mixture from the fibers or sheet materials contacted therewith, so that at least the quantity required for reaction is still present, and treating the fibers or sheet materials containing the remainder of the aqueous alkaline reaction mixture with heat energy. This patent also relates to equipment for performing the process.
Carboxymethyl cellulose (CMC) fibers are manufactured by reacting a starting cellulose with an alkaline solution containing an etherifying agent dissolved therein while the cellulose is filled in a reactor and the solution is circulating by a pump so as to come into continuous contact with the cellulose, according to U.S. Pat. No. 4,410,694.
It would be desirable to find alternative methods for converting cellulose into simple sugars, such as glucose, particularly if those methods were cost effective and/or could be implemented in continuous or other large scale processes.